The present invention relates to a new and improved starterless circuit arrangement for the firing or ignition and the operation of one or a number of series connected, low voltage fluorescent lamps which are connected with a stray field transformer coupled with a voltage source, the stray field transformer generating the no-load or open-circuit voltage required for the ignition of the lamps and possessing heating coils or windings which are connecting with the electrodes of the lamps.
In order to obtain satisfactory longevity of the lamps it is important that prior to the occurrence of the discharge the lamp electrodes are pre-heated to a minimum temperature in the order of about 600.degree.C to 800.degree.C.
As is known the lamp ignition voltage, apart from the proper pre-heating of the electrodes, is furthermore dependent upon many additional factors, such as for instance the ambient temperature, the humidity of the air, the spacing between the lamp and metallic base, the aging condition, the make of the lamps, just to mention a few of the more important factors.
If it is desired to always have sufficient operational reliability, then it is necessary to select the no-load voltage to be so great that even under the most unfavorable operating conditions with a lamp which does not wish to ignite and in the presence of undervoltage there is insured for positive ignition or firing. This has the result that in the case of normal operating conditions with good lamps the ignition occurs without sufficient pre-heating. There thus occur the so-called cold starts which markedly reduce the longevity of the lamps. This dependency of the pre-heating, no-load voltage and lamp longevity is considered to be disadvantageous with the previous starterless circuits.